Suppose Malthus were right. What would you see looking back over a 2 million year period? You wouldn’t see 40 trillion people alive today. You’d see repeated cycles of boom-bust: Population growth, overpopulation, population crash.
And this is not what we see! Please take note of the Hanson quote in my original.
If you could state how the observation would differ if Malthus were wrong vs. if Malthus were right, I might listen to you.
If Malthus were wrong, we could expect to see any number of things that don’t involve growth-overpopulation-crash cycles. For example, we might see slow and steady population growth with very irregular population crashes which correspond with major natural disasters (which are responsible for sudden, large, discontinuous declines in the available food supply). In this particular scenario, we would expect to see very few human fossils that show signs of malnutrition. Whereas if Malthus had been right, we would expect to see much more fluctuation in population levels, and therefore a proportionally high number of human fossils with signs of malnutrition, because deadly famines would be proportionally more common.
And whether or not JanetK thinks I am naive, archaeologists have not found very many malnourished human fossils. Furthermore, if Malthus had been right, we should expect to see most modern forager tribes having at least occasional difficulties getting enough to eat. We should likewise see heavy fluctuation of prey animal populations in the vicinity of human hunter-gatherers.
The Lotka-Volterra equation may do a wonderful job of explaining simple predator-prey relationships, but it assumes exponential growth of the prey population, which is exactly what I’m disputing. [ETA: I took a closer look at the Wikipedia page and noticed that the LV equation also assumes that “the prey population finds ample food at all times.” Removing predators from this equation doesn’t give you Malthus. It gives you infinite growth forever.]
The way Malthus was wrong was in not observing that viruses and pathogenic bacteria are predators of humans.
Disease epidemics as we currently imagine them did not exist pre-agriculture. Small, widely-dispersed human populations can’t support a sustainable population of bacteria or viruses. The rate of transmission is too low.
The Lotka-Volterra equation may do a wonderful job of explaining simple predator-prey relationships, but it assumes exponential growth of the prey population, which is exactly what I’m disputing.
I’ve got a book somewhere (small trade paperback, dull silver cover[1], title might be Life) which claims that no one has ever gotten those pretty predator-prey equations to cycle nicely in the real world, not even with two species of micro-organisms in a test tube.
The Wiki page for the equation didn’t seem to mention real-world examples.
I’ll update with more detail if I find the book.
[1] It’s a shame amazon doesn’t have searches based on the way people really remember books.
The Wikipedia page does mention the wolf and moose populations in Isle Royale National Park as its sole real-world example. The paper it cites, though, doesn’t seem to find the LV equation to be among the most useful available models, which is a pretty bad sign for its actual descriptive power.
I’ve got a book somewhere (small trade paperback, dull silver cover[1], title might be Life) which claims that no one has ever gotten those pretty predator-prey equations to cycle nicely in the real world, not even with two species of micro-organisms in a test tube.
With 3 species, the LK equation can become chaotic, so I wouldn’t expect to be able to duplicate a real-world history even if the model were perfect.
Perhaps we could find a 2-species real-world LK case involving bacteria deep underground.
You’d see repeated cycles of boom-bust: Population growth, overpopulation, population crash.
And this is not what we see! Please take note of the Hanson quote in my original.
It isn’t? What would we see that would be different? Do you expect to be able to pick out boom-bust cycles that occur in 3 or 4 generations, in a fossil record going back 2 million years?
In this particular scenario, we would expect to see very few human fossils that show signs of malnutrition. Whereas if Malthus had been right, we would expect to see much more fluctuation in population levels, and therefore a proportionally high number of human fossils with signs of malnutrition, because deadly famines would be proportionally more common.
This is an interesting point. You’d have to do the math to figure out how many malnourished fossils we would expect to find.
The Lotka-Volterra equation may do a wonderful job of explaining simple predator-prey relationships, but it assumes exponential growth of the prey population, which is exactly what I’m disputing.
Yes; which is why I mention the Lotka-Volterra equation, and its general acceptance by biologists, as evidence that you are wrong.
Disease epidemics as we currently imagine them did not exist pre-agriculture. Small, widely-dispersed human populations can’t support a sustainable population of bacteria or viruses. The rate of transmission is too low.
Okay. You got me. Malthus was completely right pre-agriculture.
No, seriously. You just said that hunter-gatherers had no viruses or bacteria. Then why did they have immune systems?
Agricultural communities, and people with animals, and people living in towns, had progressively increasing numbers of parasites, and more dramatic boom-crash cycles, true.
The important point is that hunter-gatherers reached “carrying capacity” before humans even evolved; so you wouldn’t expect to see exponential growth, ever. This is a general truth: Species don’t exist at far-below-carrying-capacity levels, except after a population crash, or on introduction into a new environment. For a fair test of Malthus, you should look at the population growth on introducing a new species into an environment where it has no predators. The introduction of cane toads and rabbits into Australia would be perfect case studies. And, they show Malthus was right.
Also remember that carrying capacity increases with technology. It is not correct to assume that there was no growth in technology before agriculture! Some hunter-gatherers have thousands of impressive technological achievements. “Hunter-gatherer” is not a single level of technology. Just enumerating the number of different snares or traps in the repertoire of some 19th century Native Americans would get you to around 100 technological devices, none of which most college graduates would be able to invent independently. Tanning deer hide required 6 major technical innovations. Flintknapping is a skill similar to playing chess; it requires memorizing countless patterns of rock ledges and lumps, and predicting what will happen several moves ahead. Likewise tracking, weather prediction, and hunting. Basketweaving, cooking, firebuilding, making rope or thread, felting, dyeing, waterproofing, pottery, bow-making, flute-making, waging war—each of these involves a multitude of technological inventions that a modern-day genius would be hard-pressed to come up with on their own.
Anecdotal evidence suggests competition with other groups was the major limiting factor on first contact with Europeans in most of the now United States; while food was the major limiting factor in the far north (and starvation was extremely common).
I think you need to clarify what you mean when you say Malthus was wrong. Do you mean that population does not grow exponentially in the absence of predation or food or territory or other limitations? Then you are wrong. Do you mean that famine and population collapse is not the necessary outcome of reaching carrying capacity? Then you are right. “Carrying capacity” is harder to reach than it sounds, in the same way that running out of oil is hard. It is a limit that is a repulsor in configuration space; the closer you get to it, the harder it is to get any closer.
It isn’t? What would we see that would be different? Do you expect to be able to pick out boom-bust cycles that occur in 3 or 4 generations, in a fossil record going back 2 million years?
WrongBot:
If Malthus were wrong, we could expect to see any number of things that don’t involve growth-overpopulation-crash cycles. For example, we might see slow and steady population growth with very irregular population crashes which correspond with major natural disasters (which are responsible for sudden, large, discontinuous declines in the available food supply). In this particular scenario, we would expect to see very few human fossils that show signs of malnutrition. Whereas if Malthus had been right, we would expect to see much more fluctuation in population levels, and therefore a proportionally high number of human fossils with signs of malnutrition, because deadly famines would be proportionally more common.
Since I guess I wasn’t sufficiently clear: each bust generation should contain a high percentage of individuals who die of starvation or are significantly malnourished during their childhood. For simplicity’s sake I’ll make an incredibly generous assumption that that percentage is 10%, though I’d expect it to be much higher in reality. If one in every four generations is a bust, then that’s 2.5% of all humans in the past 2 million years whose skeletons would show significant signs of malnourishment. But the fossil record contains many fewer malnourished humans than that already conservative figure!
PhilGoetz:
Yes; which is why I mention the Lotka-Volterra equation, and its general acceptance by biologists, as evidence that you are wrong.
Please see the edit to my earlier post. The Lotka-Volterra equation assumes infinite food.
Please also see this link, which JoshuaZ posted. Key quote:
Are such cyclic systems common in Nature? No. How well does the model predict population changes in the real world? Not well, and some of its shortcomings are apparent.
PhilGoetz:
No, seriously. You just said that hunter-gatherers had no viruses or bacteria. Then why did they have immune systems?
Yeah, my bad. I stand by what I said about epidemics, but that bit is obviously wrong.
I don’t think food shortages necessarily leave malnourished fossils behind. Two other things could happen: people could run out of stored food during winter and freeze to death; or people could detect a food shortage coming, and fight over supplies until the population is small enough to support.
Yes; which is why I mention the Lotka-Volterra equation, and its general acceptance by biologists, as evidence that you are wrong.
Please see the edit to my earlier post. The Lotka-Volterra equation assumes infinite food.
But do you understand how biologists use it, and for what uses they accept it? Or is your explanation “well, biologists are stupid, duh”?
If you’re going to go around saying the methods and conclusions in a particular domain are wrong, you need a quite deep understanding of that domain. So far, you haven’t given that impression in your posts on Malthus.
And this is not what we see! Please take note of the Hanson quote in my original.
If Malthus were wrong, we could expect to see any number of things that don’t involve growth-overpopulation-crash cycles. For example, we might see slow and steady population growth with very irregular population crashes which correspond with major natural disasters (which are responsible for sudden, large, discontinuous declines in the available food supply). In this particular scenario, we would expect to see very few human fossils that show signs of malnutrition. Whereas if Malthus had been right, we would expect to see much more fluctuation in population levels, and therefore a proportionally high number of human fossils with signs of malnutrition, because deadly famines would be proportionally more common.
And whether or not JanetK thinks I am naive, archaeologists have not found very many malnourished human fossils. Furthermore, if Malthus had been right, we should expect to see most modern forager tribes having at least occasional difficulties getting enough to eat. We should likewise see heavy fluctuation of prey animal populations in the vicinity of human hunter-gatherers.
The Lotka-Volterra equation may do a wonderful job of explaining simple predator-prey relationships, but it assumes exponential growth of the prey population, which is exactly what I’m disputing. [ETA: I took a closer look at the Wikipedia page and noticed that the LV equation also assumes that “the prey population finds ample food at all times.” Removing predators from this equation doesn’t give you Malthus. It gives you infinite growth forever.]
Disease epidemics as we currently imagine them did not exist pre-agriculture. Small, widely-dispersed human populations can’t support a sustainable population of bacteria or viruses. The rate of transmission is too low.
I’ve got a book somewhere (small trade paperback, dull silver cover[1], title might be Life) which claims that no one has ever gotten those pretty predator-prey equations to cycle nicely in the real world, not even with two species of micro-organisms in a test tube.
The Wiki page for the equation didn’t seem to mention real-world examples.
I’ll update with more detail if I find the book.
[1] It’s a shame amazon doesn’t have searches based on the way people really remember books.
The Wikipedia page does mention the wolf and moose populations in Isle Royale National Park as its sole real-world example. The paper it cites, though, doesn’t seem to find the LV equation to be among the most useful available models, which is a pretty bad sign for its actual descriptive power.
With 3 species, the LK equation can become chaotic, so I wouldn’t expect to be able to duplicate a real-world history even if the model were perfect.
Perhaps we could find a 2-species real-world LK case involving bacteria deep underground.
This source claims that some real life examples have actually done this correctly including the archetypal rabbit/lynx example.
Upvoted for your footnote :)
It isn’t? What would we see that would be different? Do you expect to be able to pick out boom-bust cycles that occur in 3 or 4 generations, in a fossil record going back 2 million years?
This is an interesting point. You’d have to do the math to figure out how many malnourished fossils we would expect to find.
Yes; which is why I mention the Lotka-Volterra equation, and its general acceptance by biologists, as evidence that you are wrong.
Okay. You got me. Malthus was completely right pre-agriculture.
No, seriously. You just said that hunter-gatherers had no viruses or bacteria. Then why did they have immune systems?
Agricultural communities, and people with animals, and people living in towns, had progressively increasing numbers of parasites, and more dramatic boom-crash cycles, true.
The important point is that hunter-gatherers reached “carrying capacity” before humans even evolved; so you wouldn’t expect to see exponential growth, ever. This is a general truth: Species don’t exist at far-below-carrying-capacity levels, except after a population crash, or on introduction into a new environment. For a fair test of Malthus, you should look at the population growth on introducing a new species into an environment where it has no predators. The introduction of cane toads and rabbits into Australia would be perfect case studies. And, they show Malthus was right.
Also remember that carrying capacity increases with technology. It is not correct to assume that there was no growth in technology before agriculture! Some hunter-gatherers have thousands of impressive technological achievements. “Hunter-gatherer” is not a single level of technology. Just enumerating the number of different snares or traps in the repertoire of some 19th century Native Americans would get you to around 100 technological devices, none of which most college graduates would be able to invent independently. Tanning deer hide required 6 major technical innovations. Flintknapping is a skill similar to playing chess; it requires memorizing countless patterns of rock ledges and lumps, and predicting what will happen several moves ahead. Likewise tracking, weather prediction, and hunting. Basketweaving, cooking, firebuilding, making rope or thread, felting, dyeing, waterproofing, pottery, bow-making, flute-making, waging war—each of these involves a multitude of technological inventions that a modern-day genius would be hard-pressed to come up with on their own.
Anecdotal evidence suggests competition with other groups was the major limiting factor on first contact with Europeans in most of the now United States; while food was the major limiting factor in the far north (and starvation was extremely common).
I think you need to clarify what you mean when you say Malthus was wrong. Do you mean that population does not grow exponentially in the absence of predation or food or territory or other limitations? Then you are wrong. Do you mean that famine and population collapse is not the necessary outcome of reaching carrying capacity? Then you are right. “Carrying capacity” is harder to reach than it sounds, in the same way that running out of oil is hard. It is a limit that is a repulsor in configuration space; the closer you get to it, the harder it is to get any closer.
PhilGoetz:
WrongBot:
Since I guess I wasn’t sufficiently clear: each bust generation should contain a high percentage of individuals who die of starvation or are significantly malnourished during their childhood. For simplicity’s sake I’ll make an incredibly generous assumption that that percentage is 10%, though I’d expect it to be much higher in reality. If one in every four generations is a bust, then that’s 2.5% of all humans in the past 2 million years whose skeletons would show significant signs of malnourishment. But the fossil record contains many fewer malnourished humans than that already conservative figure!
PhilGoetz:
Please see the edit to my earlier post. The Lotka-Volterra equation assumes infinite food.
Please also see this link, which JoshuaZ posted. Key quote:
PhilGoetz:
Yeah, my bad. I stand by what I said about epidemics, but that bit is obviously wrong.
I don’t think food shortages necessarily leave malnourished fossils behind. Two other things could happen: people could run out of stored food during winter and freeze to death; or people could detect a food shortage coming, and fight over supplies until the population is small enough to support.
But do you understand how biologists use it, and for what uses they accept it? Or is your explanation “well, biologists are stupid, duh”?
If you’re going to go around saying the methods and conclusions in a particular domain are wrong, you need a quite deep understanding of that domain. So far, you haven’t given that impression in your posts on Malthus.